For nearly 40 years, Bonnie Raitt has felt and embraced the power of blues music, paying tribute to blues greats with her own engaging take on the genre that "goes all over the place," enhanced by passionate singing and tasteful slide-guitar work.

On Sunday night, her fans experienced that power times two at Frederik Meijer Gardens and Sculpture Park, with one of those blues greats -- Taj Mahal -- joining the ride, delivering a more than memorable double bill to close out the Gardens summer concert season.

One only needs to picture the scene at the tail-end of the night to understand that power: Raitt, Mahal and both their bands together on stage (11 musicians in all) creating jubilant blues-steeped strains on "Tramp" and "She Caught the Katy (and Left Me a Mule to Ride)" with the sold-out crowd of 1,750-plus on its feet, bobbing and roaring its approval.

4 OUT OF 4 STARS

Bonnie Raitt and Taj Mahal

Highlight No. 1: Raitt following up two terrific acoustic duets with Mahal by singing a mesmerizing version of John Prine's "Angel from Montgomery."Highlight No. 2: The bluesy, reggae-tinged "Love So Strong," played by both bands during the encore. Time on stage: 2 hours, 32 minutes

Let's just say it was as close to a perfect ending for a summer concert series as it gets.

Even Raitt couldn't contain her enthusiasm for the outdoor amphitheater, the weather, the sculptures, the lighting, even the Gardens' food, complimenting all of the above at different times during the evening. "Could you get anymore beautiful a place than this to play?" she gushed early on, then later, "No mosquitoes. I love this place!" And, "This is unbelievable."

She was right. Taj Mahal told me last week that the co-headlining "BonTaj Roulet" summer tour has been "an opportunity for us to make a real good thing in terms of the power of the music." Well, that "real good thing" was really, really good for much of the evening, with the 59-year-old Raitt in flawless voice and the 67-year-old Mahal obviously energized by the pair's partnership.

Bonnie Raitt performs Sunday at Frederik Meijer Gardens.

It all started with Mahal and the Phantom Blues Band's opening 47-minute set, which covered the gamut of the singer and multi-instrumentalist's blues catalog, from a rendition of Fats Domino's "Hello Josephine" to Mahal's own "Farther on Down the Road (You Will Accompany Me)" to Horace Silver's "Senor Blues," with its hard-bop, Latin-jazz milieu.

Blues music has "so many different styles and colors it ain't blue no more," Mahal explained after the slow-cookin' blues of "Here in the Dark," a tune that spotlighted the emotional intensity of the singer's voice.

Still, when it comes to voices, few in blues, rock or pop can match that of Raitt, whether she's singing the painfully poignant ballad "I Can't Make You Love Me" or the funky blues-rocker "Love Sneaking Up On You."

As demonstrated frequently Sunday night, Raitt -- who even gave shout-outs from the stage to local fans/pals, including record store owner Mario Leon and pop singer Casey Stratton -- has that singular ability and clarity of voice to make you feel like she's singing directly to you, making you feel every note and sentiment on "Angel From Montgomery" or "I Will Not Be Broken."

Then there's the redhead's slyly sexual side which emerges on uptempo crowd favorites "Something to Talk About" and "Thing Called Love," her restrained yet always classy slide-guitar work enhanced by Ricky Peterson's impressive, clutch keyboard work and solid contributions from George Marinelli on guitar, Hutch Hutchinson on bass and Ricky Fataar on drums.

And when Raitt brought out Mahal and his six-piece band (including the Texicali Horns section of saxophonist Joe Sublett and trumpet player Darrell Leonard) for a seven-song encore of duets, described as the show's "third act," it was nothing if not a delicious, bluesy feast.

Marinelli and the Phantom Blues Band's Johnny Lee Schell exchanged zesty guitar licks on "Love So Strong" and "Gnawin' on It," while a smiling Raitt and Mahal boogied with each other and traded lead vocals, finishing things up with a frisky rendering of Big Joe Turner's "TV Mama."

Just before Raitt took her final bows with the ensemble and left the stage, she termed the collaboration with Mahal and his band "a match made in heaven."